Methacrylic resin composition and injection-molded article

Active Publication Date: 2019-02-14

KURARAY CO LTD

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AI-Extracted Technical Summary

Problems solved by technology

However, application of these methods to a methacrylic resin would cause re...

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Method used

[0028]The chain transfer agent used in the present invention is not limited. Examples thereof can include mercaptan chain transfer agents such as n-octyl mercaptan, n-dodecyl mercaptan and the like; α-methyl styrene dimer; terpinolene and the like. Use of the chain transfer agent in a slightly large amount tends to cause a reduction in the absolute value of ΔYI of the methacrylic resin composition of the present invention and an increase in the flowability thereof. To reduce the absolute value of ΔYI and increase the flowability, n-octyl mercaptan, for example, is used preferably in an amount of not less than 0.3 part by mass and not more than 0.6 part by mass, more preferably in an amount of not less than 0.41 part by mass and not more than 0.55 part by mass with respect to a total of 100 parts by mass of the monomers.

[0030]An antioxidant has an effect of singly preventing oxidative degradation of a resin in the presence of oxygen. Examples thereof can include phosphorus antioxidants, hindered phenol antioxidants, thioether antioxidants and the like. To prevent degradation of optical characteristics due to coloring, use of a phosphorus antioxidant or hindered phenol antioxidant is preferred, and combined use of a phosphorus antioxidant and a hindered phenol antioxidant is more preferred.

[0037]A heat deterioration inhibitor is able to prevent heat deterioration of a resin by trapping polymer radicals generated when the r...

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Benefits of technology

[0015]The methacrylic resin composition of the present invention has excellent flowability and is less likely to cause molding defects such as silver streaks, cracks, sink marks, flow marks, resin burning, gas contamination, or coloring. The methacrylic resin composition of the present invention is also suitable for injection molding. The methacrylic resin composition of the present invention is also suitable for obtaining a thin shaped product, for example, a board having a thickness of 1 mm or less. A shaped product formed of the methacrylic resin composition of the present invention has high heat resistance and high mechanical strength and has no appearance defect such as coloring. The methacrylic resin composition of the present invention generates low shear heat when injection-molded and can be injection-molded even at low temperature and high injection pressure. Thus, a shaped product having good appearance is obtained.

[0016]A methacrylic resin composition of the present invention comprises a methacrylic resin. The content of the methacrylic resin in the methacrylic resin composition of the present invention is not less than 90% by mass, preferably 90 to 99.9% by mass, more preferably 90 to 99.5% by mass.

[0017]A methacrylic resin used in the present invention comprises methyl methacrylate m...

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Abstract

A methacrylic resin composition comprising not less than 90% by mass of a methacrylic resin, wherein the methacrylic resin comprises 95 to 100% by mass of methyl methacrylate monomer units and 0 to 5% by mass of acrylate monomer units, the methacrylic resin has an Mw of 57000 to 90000, Mw representing a weight-average molecular weight, and a ratio Mw/Mn of not more than 1.9, Mn representing a number-average molecular weight, the methacrylic resin composition has an absolute value of a difference between YI4 and YI2 of not more than 3, YI4 representing a yellow index at an optical path length of 200 mm of an injection-molded article obtained at a cylinder temperature of 280° C. in a molding cycle of 4 minutes, YI2 representing a yellow index at an optical path length of 200 mm of an injection-molded article obtained at a cylinder temperature of 280° C. in a molding cycle of 2 minutes, and meets a relationship represented by Formula (B) and Formula (C):

R≥11 Formula (B)

0.8<R/E<1.2 Formula (C)

where R represents the melt flow rate of the methacrylic resin composition as measured at 230° C. under a load of 3.8 kg, the melt flow rate R being expressed in g/10 min; and E represents a value calculated by Formula (A), the value E being expressed in g/10 min, the Formula (A) being E=exp (0.17112×W−0.00399×P+5.09713) where W represents the ratio of acrylate monomer units to the total monomer units in the methacrylic resin, the ratio W being expressed in % by mass; and P represents the degree of polymerization of the methacrylic resin.

Technology Topic

Methyl methacrylateOptical path length +5

Examples

Experimental program(3)

Example

EXAMPLES 1 TO 4 AND COMPARATIVE EXAMPLES 1 TO 8

[0100]Purified methyl methacrylate (MMA), methyl acrylate (MA), 2,2′-azobis(2-methylpropionitrile) (AIBN), and n-octyl mercaptan (n-OM) were charged into a stirrer-equipped autoclave A at ratios described in Tables 1 and 2 and dissolved uniformly to obtain starting material liquids (I).

[0101]The starting material liquid (I) was fed from the autoclave A to a tank reactor whose temperature was controlled to 140° C., at 1.5 kg/hr. Bulk polymerization was performed for a mean residence time of 120 minutes, and the reaction solution containing a polymer was continuously discharged from the tank reactor. The polymerization conversion ratio of the obtained polymer was 57% by mass.

[0102]Then, the reaction solution was heated to 230° C. and fed to a twin-screw extruder whose temperature was controlled to 240° C. A volatile component containing unreacted monomers as a main component was separated and removed in the twin-screw extruder, and the polymer was extruded as a strand. The strand is cut using a pelletizer to give resin pellets. With respect to the resin pellets, the weight average molecular weight Mw, the molecular weight distribution Mw/Mn, the ratio W of MA units, the degree of polymerization P, the melt flow rate R, and the yellow index difference ΔYI were measured. Also, the resin pellets were evaluated for injection moldability, flowability, and mold stain. The evaluation results are shown in Tables 1 and 2.

TABLE 1 Ex. Comp. Ex. 1 2 3 4 1 2 3 Starting material liq.(I) MMA [parts by mass] 94.2 94.2 96.0 96.0 92.8 92.8 92.8 MA [parts by mass] 5.8 5.8 4.0 4.0 7.2 7.2 7.2 n-OM [part by mass] 0.43 0.54 0.56 0.40 0.62 0.43 0.36 AIBN [part by mass] 0.006 0.006 0.006 0.006 0.006 0.006 0.006 methacryic resin properties Mw 73000 60000 58000 78000 53000 73000 85000 Mw/Mn 1.8 1.8 1.8 1.8 1.8 1.8 1.8 W [% by mass] 4.4 4.4 3.0 3.0 5.5 5.5 5.5 P 750 620 600 800 550 750 870 E [g/10 min] *1 17.4 29.3 24.9 11.2 46.7 21.0 13.0 methacrylic resin composition properties R [g/10 min] 15.0 33.0 27.0 12.0 51.0 20.0 14.0 R/E 0.86 1.13 1.08 1.07 1.09 0.95 1.07 ΔYI 2.4 2.6 2.7 2.8 3.5 3.7 3.6 shaped product evaluation injection moldability ∘ ∘ ∘ ∘ x ∘ ∘ mold stain ∘ ∘ ∘ ∘ ∘ ∘ ∘ flowability ∘ ∘ ∘ ∘ ∘ ∘ ∘ *1 E = exp (0.17112 × W − 0.00399 × P + 5.09713)

Example

COMPARATIVE EXAMPLE 9

[0103]Purified methyl methacrylate, methyl acrylate, 2,2′-azobis (2-methylpropionitrile), and n-octyl mercaptan were charged into a stirrer-equipped autoclave A at a ratio described in Table 2 and dissolved uniformly to obtain a starting material liquid (I).

[0104]Also, 2,2′-azobis (2-methylpropionitrile) and n-octyl mercaptan were charged into an autoclave B at a ratio described in Table 2 and dissolved with a slight amount of methyl methacrylate to obtain a starting material liquid (II).

[0105]The starting material liquid (I) was fed to a first tank reactor whose temperature was controlled to 140° C., at 1.5 kg/hr, and bulk polymerization was performed for a mean residence time of 90 minutes. A reaction solution (a) containing a polymer was continuously discharged from the first tank reactor at 1.5 kg/hr. The polymerization conversion ratio of the obtained polymer was 35% by mass, and the degree of polymerization was 870.

[0106]The reaction solution (a) held at 140 ° C. and starting material liquid (II) were mixed and fed to a second tank reactor whose temperature was controlled to 140° C., at 1.5 kg/hr. Bulk polymerization was performed for a mean residence time of 90 minutes, and the reaction solution (b) containing a polymer was discharged from the second tank reactor at 1.5 kg/hr. The polymerization conversion ratio of the obtained polymer was 57% by mass.

[0107]Then, the reaction solution (b) was heated to 230° C. and fed to a twin-screw extruder whose temperature was controlled to 240° C. A volatile component containing unreacted monomers as a main component was separated and removed in the twin-screw extruder, and a polymer was extruded as a strand. The strand is cut using a pelletizer to give resin pellets. With respect to the resin pellets, the weight-average molecular weight Mw, the molecular weight distribution Mw/Mn, the ratio W of MA units, the degree of polymerization P, the melt flow rate R, and the yellow index difference ΔYI were measured. Also, the resin pellets were evaluated for injection molding, flowability, and mold stain. The results are shown in Table 2.

Example

[0108]Resin pellets were obtained in the same manner as in Example 1 except that when separating and removing a volatile component containing unreacted monomers as a main component in the twin-screw extruder and extruding a polymer as a strand, 0.40 part by mass of stearyl alcohol and 0.10 part by mass of stearic acid monoglyceride were added to 100 parts by mass of the polymer. With respect to the resin pellets, the weight-average molecular weight Mw, the molecular weight distribution Mw/Mn, the ratio W of MA units, the degree of polymerization P, the melt flow rate R, and the yellow index difference ΔYI were measured. Also, the resin pellets were evaluated for injection moldability, flowability, and mold stain. The results are shown in Table 2.

TABLE 2 Comp. Ex. 4 5 6 7 8 9 10 Starting material liq.(I) MMA [parts by mass] 94.2 96.0 96.0 94.2 94.2 94.2 94.2 MA [parts by mass] 5.8 4.0 4.0 5.8 5.8 5.8 5.8 n-OM [part by mass] 0.62 0.62 0.35 0.33 0.36 0.36 0.54 AIBN [part by mass] 0.006 0.006 0.006 0.006 0.006 0.004 0.006 Starting material liq.(II) n-OM [part by mass] 0.7 AIBN [part by mass] 0.002 methacryic resin properties Mw 53000 53000 88000 93000 85000 71000 60000 Mw/Mn 1.8 1.8 1.8 1.8 1.8 2.1 1.8 W [% by mass] 4.4 3.0 3.0 4.4 4.4 4.4 4.4 P 550 550 900 950 870 730 620 E [g/10 min] *1 38.7 30.4 7.5 7.8 10.8 18.9 29.3 methacrylic resin composition properties R [g/10 min] 42.0 32.0 7.0 7.9 10.0 32.0 36.0 R/E 1.09 1.05 0.93 1.01 0.93 1.70 1.23 ΔYI 2.3 2.3 2.9 2.5 2.6 3.0 2.9 shaped product evaluation injection moldability x x Δ Δ ∘ x ∘ mold stain ∘ ∘ ∘ ∘ ∘ ∘ x flowability ∘ ∘ x x x ∘ ∘ *1 E = exp (0.17112 × W − 0.00399 × P + 5.09713)

[0109]The resin compositions obtained in Examples 1 to 4 had high flowability, excellent injection moldability, and no mold stain. As a result, the shaped products obtained in Examples 1 to 4 were excellent in transparency, heat resistance, mechanical strength, appearance, and the like. On the other hand, the resin compositions obtained in Comparative Examples 1 to 10 had low flowability, or poor injection moldability, or mold stain. As a result, with respect to the shaped products obtained in Comparative Examples 1 to 10, at least one of heat resistance, mechanical strength, appearance, and the like was poor.

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PUM

Property	Measurement	Unit
Temperature	230.0	°C
Temperature	280.0	°C
Weight	3.8	kg
tensile		MPa
Particle size		Pa
strength	10

Description & Claims & Application Information

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Classification and recommendation of technical efficacy words

Excellent flowability
High heat resistance

Methacrylic resin composition and injection-molded article

AI-Extracted Technical Summary

Problems solved by technology

Method used

Benefits of technology

Abstract

Examples

Example

Example

Example

PUM

Description & Claims & Application Information

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